This research will better define the interactions of the renal hormones in the control of renin releases and control of blood pressure and their role in hypertension. 1) The temporal relationships of the prostaglandin, kallikrein, catecholamines, and the renin-angiotensin system will be determined in the one kidney, one clip renovascular hypertensive dog. 2) These same hormone systems will also be evaluated in renovascular hypertension in man and 3) in patients with essential hypertension with low, medium and high renin.